Nodule carbohydrate metabolism and polyols involvement in the response of Medicago sativa to salt stress |
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| Affiliation: | 1. Departamento de Agronomía, Universidad de Córdoba-Campus de Excelencia Internacional Agroalimentario ceiA3, Edificio C4, Campus de Rabanales, 14014 Córdoba, Spain;2. Instituto de Agricultura Sostenible, IAS-CSIC, 14080 Córdoba, Spain;3. Department of Ecology and Evolutionary Biology, U.C. Irvine, CA, USA;1. Departamento de Ecoloxía e Bioloxía Animal, Universidade de Vigo, Campus Lagoas-Marcosende, 36310 Vigo, Spain;2. Centre for Ecology and Evolution in Microbial Model Systems – EEMiS, Linnaeus University, SE-39182 Kalmar, Sweden;3. IIM-CSIC, Insituto de InvestigaciónsMariñas, Eduardo Cabello 6, 36208 Vigo, Spain;4. School of Environmental Science, University of East Anglia, Norwich NR4 7TJ, UK;1. Consiglio per la ricerca in agricoltura e l''analisi dell''economia agraria, Centro di Ricerca per l’Agrumicoltura e le Colture Mediterranee (CREA-ACM), Corso Savoia, 190-95024 Acireale (CT), Italy;2. Consiglio per la ricerca in agricoltura e l''analisi dell''economia agraria, Centro di ricerca per l’olivicoltura e l’industria olearia (CREA-OLI), C.da Li Rocchi-Vermicelli, 87036 Rende (CS), Italy;3. Università della Calabria, Dipartimento di Farmacia, Scienze della Salute e della Nutrizione, Ed. Polifunzionale, 87036 Arcavacata di Rende (CS), Italy;1. Department of Geography, University at Buffalo, USA;2. Department of Geography, Brigham Young University, USA;3. Cranfield Soil and Agrifood Institute, Cranfield University, UK;4. Agronomy and Soils Department, Auburn University, USA;5. United States Department of Agriculture-Agricultural Research Service, Tifton, USA |
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| Abstract: | Alterations of plant growth, chlorophyll fluorescence parameters, nodule carbon metabolism and polyols concentration as result of salt stress were examined in alfalfa (Medicago sativa). Plants, in symbiosis with Sinorhizobium meliloti GR4 strain, were grown under controlled conditions for 35 days (DAS) and subjected to 150 mM of NaCl stress. Plant biomass (PDW) and nitrogen fixation rate (NFR) were markedly affected by salt stress conditions; the highest reductions of PDW (50%) and NFR (40%) were registered at 84 DAS and 56 DAS, respectively. In addition, salinity affected the chlorophyll fluorescence parameters, decreased initial chlorophyll fluorescence (F0) and increased the optimum quantum yield of PSII (Fv/Fm ratio). The enzyme activities sucrose synthase activity and phosphoenolpyruvate carboxylase, responsible for the carbon supply to the bacteroids by the formation of dicarboxylates, were drastically inhibited by salinity, mainly at 56 DAS with the beginning of flowering. The content of total soluble sugars and proline increased under salt stress, and these concentrations were higher in nodule than in leaf. This last result suggests that the nodule is an organ specially protected in order to maintain its functioning, even under stress conditions. Besides, the content of myoinositol and pinitol in leaves and nodules changed with the plant growth stage and the saline treatment. Under salinity stress, the concentrations of pinitol in nodule were higher than in leaf, which supports the central function of this molecule in the adaptive response of nodules to salt stress. The increase of pinitol synthesis in nodule of M. sativa under salt stress could be one of the adaptive features used by the plant. |
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